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TOMOYO Linux Cross Reference
Linux/fs/btrfs/free-space-tree.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2015 Facebook.  All rights reserved.
  4  */
  5 
  6 #include <linux/kernel.h>
  7 #include <linux/sched/mm.h>
  8 #include "ctree.h"
  9 #include "disk-io.h"
 10 #include "locking.h"
 11 #include "free-space-tree.h"
 12 #include "transaction.h"
 13 
 14 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
 15                                         struct btrfs_block_group_cache *block_group,
 16                                         struct btrfs_path *path);
 17 
 18 void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
 19 {
 20         u32 bitmap_range;
 21         size_t bitmap_size;
 22         u64 num_bitmaps, total_bitmap_size;
 23 
 24         /*
 25          * We convert to bitmaps when the disk space required for using extents
 26          * exceeds that required for using bitmaps.
 27          */
 28         bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
 29         num_bitmaps = div_u64(cache->key.offset + bitmap_range - 1,
 30                               bitmap_range);
 31         bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
 32         total_bitmap_size = num_bitmaps * bitmap_size;
 33         cache->bitmap_high_thresh = div_u64(total_bitmap_size,
 34                                             sizeof(struct btrfs_item));
 35 
 36         /*
 37          * We allow for a small buffer between the high threshold and low
 38          * threshold to avoid thrashing back and forth between the two formats.
 39          */
 40         if (cache->bitmap_high_thresh > 100)
 41                 cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
 42         else
 43                 cache->bitmap_low_thresh = 0;
 44 }
 45 
 46 static int add_new_free_space_info(struct btrfs_trans_handle *trans,
 47                                    struct btrfs_block_group_cache *block_group,
 48                                    struct btrfs_path *path)
 49 {
 50         struct btrfs_root *root = trans->fs_info->free_space_root;
 51         struct btrfs_free_space_info *info;
 52         struct btrfs_key key;
 53         struct extent_buffer *leaf;
 54         int ret;
 55 
 56         key.objectid = block_group->key.objectid;
 57         key.type = BTRFS_FREE_SPACE_INFO_KEY;
 58         key.offset = block_group->key.offset;
 59 
 60         ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
 61         if (ret)
 62                 goto out;
 63 
 64         leaf = path->nodes[0];
 65         info = btrfs_item_ptr(leaf, path->slots[0],
 66                               struct btrfs_free_space_info);
 67         btrfs_set_free_space_extent_count(leaf, info, 0);
 68         btrfs_set_free_space_flags(leaf, info, 0);
 69         btrfs_mark_buffer_dirty(leaf);
 70 
 71         ret = 0;
 72 out:
 73         btrfs_release_path(path);
 74         return ret;
 75 }
 76 
 77 EXPORT_FOR_TESTS
 78 struct btrfs_free_space_info *search_free_space_info(
 79                 struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info,
 80                 struct btrfs_block_group_cache *block_group,
 81                 struct btrfs_path *path, int cow)
 82 {
 83         struct btrfs_root *root = fs_info->free_space_root;
 84         struct btrfs_key key;
 85         int ret;
 86 
 87         key.objectid = block_group->key.objectid;
 88         key.type = BTRFS_FREE_SPACE_INFO_KEY;
 89         key.offset = block_group->key.offset;
 90 
 91         ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
 92         if (ret < 0)
 93                 return ERR_PTR(ret);
 94         if (ret != 0) {
 95                 btrfs_warn(fs_info, "missing free space info for %llu",
 96                            block_group->key.objectid);
 97                 ASSERT(0);
 98                 return ERR_PTR(-ENOENT);
 99         }
100 
101         return btrfs_item_ptr(path->nodes[0], path->slots[0],
102                               struct btrfs_free_space_info);
103 }
104 
105 /*
106  * btrfs_search_slot() but we're looking for the greatest key less than the
107  * passed key.
108  */
109 static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
110                                   struct btrfs_root *root,
111                                   struct btrfs_key *key, struct btrfs_path *p,
112                                   int ins_len, int cow)
113 {
114         int ret;
115 
116         ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
117         if (ret < 0)
118                 return ret;
119 
120         if (ret == 0) {
121                 ASSERT(0);
122                 return -EIO;
123         }
124 
125         if (p->slots[0] == 0) {
126                 ASSERT(0);
127                 return -EIO;
128         }
129         p->slots[0]--;
130 
131         return 0;
132 }
133 
134 static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
135 {
136         return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
137 }
138 
139 static unsigned long *alloc_bitmap(u32 bitmap_size)
140 {
141         unsigned long *ret;
142         unsigned int nofs_flag;
143         u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
144 
145         /*
146          * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
147          * into the filesystem as the free space bitmap can be modified in the
148          * critical section of a transaction commit.
149          *
150          * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
151          * know that recursion is unsafe.
152          */
153         nofs_flag = memalloc_nofs_save();
154         ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
155         memalloc_nofs_restore(nofs_flag);
156         return ret;
157 }
158 
159 static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
160 {
161         u8 *p = ((u8 *)map) + BIT_BYTE(start);
162         const unsigned int size = start + len;
163         int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
164         u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
165 
166         while (len - bits_to_set >= 0) {
167                 *p |= mask_to_set;
168                 len -= bits_to_set;
169                 bits_to_set = BITS_PER_BYTE;
170                 mask_to_set = ~0;
171                 p++;
172         }
173         if (len) {
174                 mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
175                 *p |= mask_to_set;
176         }
177 }
178 
179 EXPORT_FOR_TESTS
180 int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
181                                   struct btrfs_block_group_cache *block_group,
182                                   struct btrfs_path *path)
183 {
184         struct btrfs_fs_info *fs_info = trans->fs_info;
185         struct btrfs_root *root = fs_info->free_space_root;
186         struct btrfs_free_space_info *info;
187         struct btrfs_key key, found_key;
188         struct extent_buffer *leaf;
189         unsigned long *bitmap;
190         char *bitmap_cursor;
191         u64 start, end;
192         u64 bitmap_range, i;
193         u32 bitmap_size, flags, expected_extent_count;
194         u32 extent_count = 0;
195         int done = 0, nr;
196         int ret;
197 
198         bitmap_size = free_space_bitmap_size(block_group->key.offset,
199                                              fs_info->sectorsize);
200         bitmap = alloc_bitmap(bitmap_size);
201         if (!bitmap) {
202                 ret = -ENOMEM;
203                 goto out;
204         }
205 
206         start = block_group->key.objectid;
207         end = block_group->key.objectid + block_group->key.offset;
208 
209         key.objectid = end - 1;
210         key.type = (u8)-1;
211         key.offset = (u64)-1;
212 
213         while (!done) {
214                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
215                 if (ret)
216                         goto out;
217 
218                 leaf = path->nodes[0];
219                 nr = 0;
220                 path->slots[0]++;
221                 while (path->slots[0] > 0) {
222                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
223 
224                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
225                                 ASSERT(found_key.objectid == block_group->key.objectid);
226                                 ASSERT(found_key.offset == block_group->key.offset);
227                                 done = 1;
228                                 break;
229                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
230                                 u64 first, last;
231 
232                                 ASSERT(found_key.objectid >= start);
233                                 ASSERT(found_key.objectid < end);
234                                 ASSERT(found_key.objectid + found_key.offset <= end);
235 
236                                 first = div_u64(found_key.objectid - start,
237                                                 fs_info->sectorsize);
238                                 last = div_u64(found_key.objectid + found_key.offset - start,
239                                                fs_info->sectorsize);
240                                 le_bitmap_set(bitmap, first, last - first);
241 
242                                 extent_count++;
243                                 nr++;
244                                 path->slots[0]--;
245                         } else {
246                                 ASSERT(0);
247                         }
248                 }
249 
250                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
251                 if (ret)
252                         goto out;
253                 btrfs_release_path(path);
254         }
255 
256         info = search_free_space_info(trans, fs_info, block_group, path, 1);
257         if (IS_ERR(info)) {
258                 ret = PTR_ERR(info);
259                 goto out;
260         }
261         leaf = path->nodes[0];
262         flags = btrfs_free_space_flags(leaf, info);
263         flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
264         btrfs_set_free_space_flags(leaf, info, flags);
265         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
266         btrfs_mark_buffer_dirty(leaf);
267         btrfs_release_path(path);
268 
269         if (extent_count != expected_extent_count) {
270                 btrfs_err(fs_info,
271                           "incorrect extent count for %llu; counted %u, expected %u",
272                           block_group->key.objectid, extent_count,
273                           expected_extent_count);
274                 ASSERT(0);
275                 ret = -EIO;
276                 goto out;
277         }
278 
279         bitmap_cursor = (char *)bitmap;
280         bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
281         i = start;
282         while (i < end) {
283                 unsigned long ptr;
284                 u64 extent_size;
285                 u32 data_size;
286 
287                 extent_size = min(end - i, bitmap_range);
288                 data_size = free_space_bitmap_size(extent_size,
289                                                    fs_info->sectorsize);
290 
291                 key.objectid = i;
292                 key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
293                 key.offset = extent_size;
294 
295                 ret = btrfs_insert_empty_item(trans, root, path, &key,
296                                               data_size);
297                 if (ret)
298                         goto out;
299 
300                 leaf = path->nodes[0];
301                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
302                 write_extent_buffer(leaf, bitmap_cursor, ptr,
303                                     data_size);
304                 btrfs_mark_buffer_dirty(leaf);
305                 btrfs_release_path(path);
306 
307                 i += extent_size;
308                 bitmap_cursor += data_size;
309         }
310 
311         ret = 0;
312 out:
313         kvfree(bitmap);
314         if (ret)
315                 btrfs_abort_transaction(trans, ret);
316         return ret;
317 }
318 
319 EXPORT_FOR_TESTS
320 int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
321                                   struct btrfs_block_group_cache *block_group,
322                                   struct btrfs_path *path)
323 {
324         struct btrfs_fs_info *fs_info = trans->fs_info;
325         struct btrfs_root *root = fs_info->free_space_root;
326         struct btrfs_free_space_info *info;
327         struct btrfs_key key, found_key;
328         struct extent_buffer *leaf;
329         unsigned long *bitmap;
330         u64 start, end;
331         u32 bitmap_size, flags, expected_extent_count;
332         unsigned long nrbits, start_bit, end_bit;
333         u32 extent_count = 0;
334         int done = 0, nr;
335         int ret;
336 
337         bitmap_size = free_space_bitmap_size(block_group->key.offset,
338                                              fs_info->sectorsize);
339         bitmap = alloc_bitmap(bitmap_size);
340         if (!bitmap) {
341                 ret = -ENOMEM;
342                 goto out;
343         }
344 
345         start = block_group->key.objectid;
346         end = block_group->key.objectid + block_group->key.offset;
347 
348         key.objectid = end - 1;
349         key.type = (u8)-1;
350         key.offset = (u64)-1;
351 
352         while (!done) {
353                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
354                 if (ret)
355                         goto out;
356 
357                 leaf = path->nodes[0];
358                 nr = 0;
359                 path->slots[0]++;
360                 while (path->slots[0] > 0) {
361                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
362 
363                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
364                                 ASSERT(found_key.objectid == block_group->key.objectid);
365                                 ASSERT(found_key.offset == block_group->key.offset);
366                                 done = 1;
367                                 break;
368                         } else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
369                                 unsigned long ptr;
370                                 char *bitmap_cursor;
371                                 u32 bitmap_pos, data_size;
372 
373                                 ASSERT(found_key.objectid >= start);
374                                 ASSERT(found_key.objectid < end);
375                                 ASSERT(found_key.objectid + found_key.offset <= end);
376 
377                                 bitmap_pos = div_u64(found_key.objectid - start,
378                                                      fs_info->sectorsize *
379                                                      BITS_PER_BYTE);
380                                 bitmap_cursor = ((char *)bitmap) + bitmap_pos;
381                                 data_size = free_space_bitmap_size(found_key.offset,
382                                                                    fs_info->sectorsize);
383 
384                                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
385                                 read_extent_buffer(leaf, bitmap_cursor, ptr,
386                                                    data_size);
387 
388                                 nr++;
389                                 path->slots[0]--;
390                         } else {
391                                 ASSERT(0);
392                         }
393                 }
394 
395                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
396                 if (ret)
397                         goto out;
398                 btrfs_release_path(path);
399         }
400 
401         info = search_free_space_info(trans, fs_info, block_group, path, 1);
402         if (IS_ERR(info)) {
403                 ret = PTR_ERR(info);
404                 goto out;
405         }
406         leaf = path->nodes[0];
407         flags = btrfs_free_space_flags(leaf, info);
408         flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
409         btrfs_set_free_space_flags(leaf, info, flags);
410         expected_extent_count = btrfs_free_space_extent_count(leaf, info);
411         btrfs_mark_buffer_dirty(leaf);
412         btrfs_release_path(path);
413 
414         nrbits = div_u64(block_group->key.offset, block_group->fs_info->sectorsize);
415         start_bit = find_next_bit_le(bitmap, nrbits, 0);
416 
417         while (start_bit < nrbits) {
418                 end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
419                 ASSERT(start_bit < end_bit);
420 
421                 key.objectid = start + start_bit * block_group->fs_info->sectorsize;
422                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
423                 key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
424 
425                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
426                 if (ret)
427                         goto out;
428                 btrfs_release_path(path);
429 
430                 extent_count++;
431 
432                 start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
433         }
434 
435         if (extent_count != expected_extent_count) {
436                 btrfs_err(fs_info,
437                           "incorrect extent count for %llu; counted %u, expected %u",
438                           block_group->key.objectid, extent_count,
439                           expected_extent_count);
440                 ASSERT(0);
441                 ret = -EIO;
442                 goto out;
443         }
444 
445         ret = 0;
446 out:
447         kvfree(bitmap);
448         if (ret)
449                 btrfs_abort_transaction(trans, ret);
450         return ret;
451 }
452 
453 static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
454                                           struct btrfs_block_group_cache *block_group,
455                                           struct btrfs_path *path,
456                                           int new_extents)
457 {
458         struct btrfs_free_space_info *info;
459         u32 flags;
460         u32 extent_count;
461         int ret = 0;
462 
463         if (new_extents == 0)
464                 return 0;
465 
466         info = search_free_space_info(trans, trans->fs_info, block_group, path,
467                                       1);
468         if (IS_ERR(info)) {
469                 ret = PTR_ERR(info);
470                 goto out;
471         }
472         flags = btrfs_free_space_flags(path->nodes[0], info);
473         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
474 
475         extent_count += new_extents;
476         btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
477         btrfs_mark_buffer_dirty(path->nodes[0]);
478         btrfs_release_path(path);
479 
480         if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
481             extent_count > block_group->bitmap_high_thresh) {
482                 ret = convert_free_space_to_bitmaps(trans, block_group, path);
483         } else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
484                    extent_count < block_group->bitmap_low_thresh) {
485                 ret = convert_free_space_to_extents(trans, block_group, path);
486         }
487 
488 out:
489         return ret;
490 }
491 
492 EXPORT_FOR_TESTS
493 int free_space_test_bit(struct btrfs_block_group_cache *block_group,
494                         struct btrfs_path *path, u64 offset)
495 {
496         struct extent_buffer *leaf;
497         struct btrfs_key key;
498         u64 found_start, found_end;
499         unsigned long ptr, i;
500 
501         leaf = path->nodes[0];
502         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
503         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
504 
505         found_start = key.objectid;
506         found_end = key.objectid + key.offset;
507         ASSERT(offset >= found_start && offset < found_end);
508 
509         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
510         i = div_u64(offset - found_start,
511                     block_group->fs_info->sectorsize);
512         return !!extent_buffer_test_bit(leaf, ptr, i);
513 }
514 
515 static void free_space_set_bits(struct btrfs_block_group_cache *block_group,
516                                 struct btrfs_path *path, u64 *start, u64 *size,
517                                 int bit)
518 {
519         struct btrfs_fs_info *fs_info = block_group->fs_info;
520         struct extent_buffer *leaf;
521         struct btrfs_key key;
522         u64 end = *start + *size;
523         u64 found_start, found_end;
524         unsigned long ptr, first, last;
525 
526         leaf = path->nodes[0];
527         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
528         ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
529 
530         found_start = key.objectid;
531         found_end = key.objectid + key.offset;
532         ASSERT(*start >= found_start && *start < found_end);
533         ASSERT(end > found_start);
534 
535         if (end > found_end)
536                 end = found_end;
537 
538         ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
539         first = div_u64(*start - found_start, fs_info->sectorsize);
540         last = div_u64(end - found_start, fs_info->sectorsize);
541         if (bit)
542                 extent_buffer_bitmap_set(leaf, ptr, first, last - first);
543         else
544                 extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
545         btrfs_mark_buffer_dirty(leaf);
546 
547         *size -= end - *start;
548         *start = end;
549 }
550 
551 /*
552  * We can't use btrfs_next_item() in modify_free_space_bitmap() because
553  * btrfs_next_leaf() doesn't get the path for writing. We can forgo the fancy
554  * tree walking in btrfs_next_leaf() anyways because we know exactly what we're
555  * looking for.
556  */
557 static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
558                                   struct btrfs_root *root, struct btrfs_path *p)
559 {
560         struct btrfs_key key;
561 
562         if (p->slots[0] + 1 < btrfs_header_nritems(p->nodes[0])) {
563                 p->slots[0]++;
564                 return 0;
565         }
566 
567         btrfs_item_key_to_cpu(p->nodes[0], &key, p->slots[0]);
568         btrfs_release_path(p);
569 
570         key.objectid += key.offset;
571         key.type = (u8)-1;
572         key.offset = (u64)-1;
573 
574         return btrfs_search_prev_slot(trans, root, &key, p, 0, 1);
575 }
576 
577 /*
578  * If remove is 1, then we are removing free space, thus clearing bits in the
579  * bitmap. If remove is 0, then we are adding free space, thus setting bits in
580  * the bitmap.
581  */
582 static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
583                                     struct btrfs_block_group_cache *block_group,
584                                     struct btrfs_path *path,
585                                     u64 start, u64 size, int remove)
586 {
587         struct btrfs_root *root = block_group->fs_info->free_space_root;
588         struct btrfs_key key;
589         u64 end = start + size;
590         u64 cur_start, cur_size;
591         int prev_bit, next_bit;
592         int new_extents;
593         int ret;
594 
595         /*
596          * Read the bit for the block immediately before the extent of space if
597          * that block is within the block group.
598          */
599         if (start > block_group->key.objectid) {
600                 u64 prev_block = start - block_group->fs_info->sectorsize;
601 
602                 key.objectid = prev_block;
603                 key.type = (u8)-1;
604                 key.offset = (u64)-1;
605 
606                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
607                 if (ret)
608                         goto out;
609 
610                 prev_bit = free_space_test_bit(block_group, path, prev_block);
611 
612                 /* The previous block may have been in the previous bitmap. */
613                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
614                 if (start >= key.objectid + key.offset) {
615                         ret = free_space_next_bitmap(trans, root, path);
616                         if (ret)
617                                 goto out;
618                 }
619         } else {
620                 key.objectid = start;
621                 key.type = (u8)-1;
622                 key.offset = (u64)-1;
623 
624                 ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
625                 if (ret)
626                         goto out;
627 
628                 prev_bit = -1;
629         }
630 
631         /*
632          * Iterate over all of the bitmaps overlapped by the extent of space,
633          * clearing/setting bits as required.
634          */
635         cur_start = start;
636         cur_size = size;
637         while (1) {
638                 free_space_set_bits(block_group, path, &cur_start, &cur_size,
639                                     !remove);
640                 if (cur_size == 0)
641                         break;
642                 ret = free_space_next_bitmap(trans, root, path);
643                 if (ret)
644                         goto out;
645         }
646 
647         /*
648          * Read the bit for the block immediately after the extent of space if
649          * that block is within the block group.
650          */
651         if (end < block_group->key.objectid + block_group->key.offset) {
652                 /* The next block may be in the next bitmap. */
653                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
654                 if (end >= key.objectid + key.offset) {
655                         ret = free_space_next_bitmap(trans, root, path);
656                         if (ret)
657                                 goto out;
658                 }
659 
660                 next_bit = free_space_test_bit(block_group, path, end);
661         } else {
662                 next_bit = -1;
663         }
664 
665         if (remove) {
666                 new_extents = -1;
667                 if (prev_bit == 1) {
668                         /* Leftover on the left. */
669                         new_extents++;
670                 }
671                 if (next_bit == 1) {
672                         /* Leftover on the right. */
673                         new_extents++;
674                 }
675         } else {
676                 new_extents = 1;
677                 if (prev_bit == 1) {
678                         /* Merging with neighbor on the left. */
679                         new_extents--;
680                 }
681                 if (next_bit == 1) {
682                         /* Merging with neighbor on the right. */
683                         new_extents--;
684                 }
685         }
686 
687         btrfs_release_path(path);
688         ret = update_free_space_extent_count(trans, block_group, path,
689                                              new_extents);
690 
691 out:
692         return ret;
693 }
694 
695 static int remove_free_space_extent(struct btrfs_trans_handle *trans,
696                                     struct btrfs_block_group_cache *block_group,
697                                     struct btrfs_path *path,
698                                     u64 start, u64 size)
699 {
700         struct btrfs_root *root = trans->fs_info->free_space_root;
701         struct btrfs_key key;
702         u64 found_start, found_end;
703         u64 end = start + size;
704         int new_extents = -1;
705         int ret;
706 
707         key.objectid = start;
708         key.type = (u8)-1;
709         key.offset = (u64)-1;
710 
711         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
712         if (ret)
713                 goto out;
714 
715         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
716 
717         ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
718 
719         found_start = key.objectid;
720         found_end = key.objectid + key.offset;
721         ASSERT(start >= found_start && end <= found_end);
722 
723         /*
724          * Okay, now that we've found the free space extent which contains the
725          * free space that we are removing, there are four cases:
726          *
727          * 1. We're using the whole extent: delete the key we found and
728          * decrement the free space extent count.
729          * 2. We are using part of the extent starting at the beginning: delete
730          * the key we found and insert a new key representing the leftover at
731          * the end. There is no net change in the number of extents.
732          * 3. We are using part of the extent ending at the end: delete the key
733          * we found and insert a new key representing the leftover at the
734          * beginning. There is no net change in the number of extents.
735          * 4. We are using part of the extent in the middle: delete the key we
736          * found and insert two new keys representing the leftovers on each
737          * side. Where we used to have one extent, we now have two, so increment
738          * the extent count. We may need to convert the block group to bitmaps
739          * as a result.
740          */
741 
742         /* Delete the existing key (cases 1-4). */
743         ret = btrfs_del_item(trans, root, path);
744         if (ret)
745                 goto out;
746 
747         /* Add a key for leftovers at the beginning (cases 3 and 4). */
748         if (start > found_start) {
749                 key.objectid = found_start;
750                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
751                 key.offset = start - found_start;
752 
753                 btrfs_release_path(path);
754                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
755                 if (ret)
756                         goto out;
757                 new_extents++;
758         }
759 
760         /* Add a key for leftovers at the end (cases 2 and 4). */
761         if (end < found_end) {
762                 key.objectid = end;
763                 key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
764                 key.offset = found_end - end;
765 
766                 btrfs_release_path(path);
767                 ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
768                 if (ret)
769                         goto out;
770                 new_extents++;
771         }
772 
773         btrfs_release_path(path);
774         ret = update_free_space_extent_count(trans, block_group, path,
775                                              new_extents);
776 
777 out:
778         return ret;
779 }
780 
781 EXPORT_FOR_TESTS
782 int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
783                                   struct btrfs_block_group_cache *block_group,
784                                   struct btrfs_path *path, u64 start, u64 size)
785 {
786         struct btrfs_free_space_info *info;
787         u32 flags;
788         int ret;
789 
790         if (block_group->needs_free_space) {
791                 ret = __add_block_group_free_space(trans, block_group, path);
792                 if (ret)
793                         return ret;
794         }
795 
796         info = search_free_space_info(NULL, trans->fs_info, block_group, path,
797                                       0);
798         if (IS_ERR(info))
799                 return PTR_ERR(info);
800         flags = btrfs_free_space_flags(path->nodes[0], info);
801         btrfs_release_path(path);
802 
803         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
804                 return modify_free_space_bitmap(trans, block_group, path,
805                                                 start, size, 1);
806         } else {
807                 return remove_free_space_extent(trans, block_group, path,
808                                                 start, size);
809         }
810 }
811 
812 int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
813                                 u64 start, u64 size)
814 {
815         struct btrfs_block_group_cache *block_group;
816         struct btrfs_path *path;
817         int ret;
818 
819         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
820                 return 0;
821 
822         path = btrfs_alloc_path();
823         if (!path) {
824                 ret = -ENOMEM;
825                 goto out;
826         }
827 
828         block_group = btrfs_lookup_block_group(trans->fs_info, start);
829         if (!block_group) {
830                 ASSERT(0);
831                 ret = -ENOENT;
832                 goto out;
833         }
834 
835         mutex_lock(&block_group->free_space_lock);
836         ret = __remove_from_free_space_tree(trans, block_group, path, start,
837                                             size);
838         mutex_unlock(&block_group->free_space_lock);
839 
840         btrfs_put_block_group(block_group);
841 out:
842         btrfs_free_path(path);
843         if (ret)
844                 btrfs_abort_transaction(trans, ret);
845         return ret;
846 }
847 
848 static int add_free_space_extent(struct btrfs_trans_handle *trans,
849                                  struct btrfs_block_group_cache *block_group,
850                                  struct btrfs_path *path,
851                                  u64 start, u64 size)
852 {
853         struct btrfs_root *root = trans->fs_info->free_space_root;
854         struct btrfs_key key, new_key;
855         u64 found_start, found_end;
856         u64 end = start + size;
857         int new_extents = 1;
858         int ret;
859 
860         /*
861          * We are adding a new extent of free space, but we need to merge
862          * extents. There are four cases here:
863          *
864          * 1. The new extent does not have any immediate neighbors to merge
865          * with: add the new key and increment the free space extent count. We
866          * may need to convert the block group to bitmaps as a result.
867          * 2. The new extent has an immediate neighbor before it: remove the
868          * previous key and insert a new key combining both of them. There is no
869          * net change in the number of extents.
870          * 3. The new extent has an immediate neighbor after it: remove the next
871          * key and insert a new key combining both of them. There is no net
872          * change in the number of extents.
873          * 4. The new extent has immediate neighbors on both sides: remove both
874          * of the keys and insert a new key combining all of them. Where we used
875          * to have two extents, we now have one, so decrement the extent count.
876          */
877 
878         new_key.objectid = start;
879         new_key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
880         new_key.offset = size;
881 
882         /* Search for a neighbor on the left. */
883         if (start == block_group->key.objectid)
884                 goto right;
885         key.objectid = start - 1;
886         key.type = (u8)-1;
887         key.offset = (u64)-1;
888 
889         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
890         if (ret)
891                 goto out;
892 
893         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
894 
895         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
896                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
897                 btrfs_release_path(path);
898                 goto right;
899         }
900 
901         found_start = key.objectid;
902         found_end = key.objectid + key.offset;
903         ASSERT(found_start >= block_group->key.objectid &&
904                found_end > block_group->key.objectid);
905         ASSERT(found_start < start && found_end <= start);
906 
907         /*
908          * Delete the neighbor on the left and absorb it into the new key (cases
909          * 2 and 4).
910          */
911         if (found_end == start) {
912                 ret = btrfs_del_item(trans, root, path);
913                 if (ret)
914                         goto out;
915                 new_key.objectid = found_start;
916                 new_key.offset += key.offset;
917                 new_extents--;
918         }
919         btrfs_release_path(path);
920 
921 right:
922         /* Search for a neighbor on the right. */
923         if (end == block_group->key.objectid + block_group->key.offset)
924                 goto insert;
925         key.objectid = end;
926         key.type = (u8)-1;
927         key.offset = (u64)-1;
928 
929         ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
930         if (ret)
931                 goto out;
932 
933         btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
934 
935         if (key.type != BTRFS_FREE_SPACE_EXTENT_KEY) {
936                 ASSERT(key.type == BTRFS_FREE_SPACE_INFO_KEY);
937                 btrfs_release_path(path);
938                 goto insert;
939         }
940 
941         found_start = key.objectid;
942         found_end = key.objectid + key.offset;
943         ASSERT(found_start >= block_group->key.objectid &&
944                found_end > block_group->key.objectid);
945         ASSERT((found_start < start && found_end <= start) ||
946                (found_start >= end && found_end > end));
947 
948         /*
949          * Delete the neighbor on the right and absorb it into the new key
950          * (cases 3 and 4).
951          */
952         if (found_start == end) {
953                 ret = btrfs_del_item(trans, root, path);
954                 if (ret)
955                         goto out;
956                 new_key.offset += key.offset;
957                 new_extents--;
958         }
959         btrfs_release_path(path);
960 
961 insert:
962         /* Insert the new key (cases 1-4). */
963         ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
964         if (ret)
965                 goto out;
966 
967         btrfs_release_path(path);
968         ret = update_free_space_extent_count(trans, block_group, path,
969                                              new_extents);
970 
971 out:
972         return ret;
973 }
974 
975 EXPORT_FOR_TESTS
976 int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
977                              struct btrfs_block_group_cache *block_group,
978                              struct btrfs_path *path, u64 start, u64 size)
979 {
980         struct btrfs_fs_info *fs_info = trans->fs_info;
981         struct btrfs_free_space_info *info;
982         u32 flags;
983         int ret;
984 
985         if (block_group->needs_free_space) {
986                 ret = __add_block_group_free_space(trans, block_group, path);
987                 if (ret)
988                         return ret;
989         }
990 
991         info = search_free_space_info(NULL, fs_info, block_group, path, 0);
992         if (IS_ERR(info))
993                 return PTR_ERR(info);
994         flags = btrfs_free_space_flags(path->nodes[0], info);
995         btrfs_release_path(path);
996 
997         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
998                 return modify_free_space_bitmap(trans, block_group, path,
999                                                 start, size, 0);
1000         } else {
1001                 return add_free_space_extent(trans, block_group, path, start,
1002                                              size);
1003         }
1004 }
1005 
1006 int add_to_free_space_tree(struct btrfs_trans_handle *trans,
1007                            u64 start, u64 size)
1008 {
1009         struct btrfs_block_group_cache *block_group;
1010         struct btrfs_path *path;
1011         int ret;
1012 
1013         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1014                 return 0;
1015 
1016         path = btrfs_alloc_path();
1017         if (!path) {
1018                 ret = -ENOMEM;
1019                 goto out;
1020         }
1021 
1022         block_group = btrfs_lookup_block_group(trans->fs_info, start);
1023         if (!block_group) {
1024                 ASSERT(0);
1025                 ret = -ENOENT;
1026                 goto out;
1027         }
1028 
1029         mutex_lock(&block_group->free_space_lock);
1030         ret = __add_to_free_space_tree(trans, block_group, path, start, size);
1031         mutex_unlock(&block_group->free_space_lock);
1032 
1033         btrfs_put_block_group(block_group);
1034 out:
1035         btrfs_free_path(path);
1036         if (ret)
1037                 btrfs_abort_transaction(trans, ret);
1038         return ret;
1039 }
1040 
1041 /*
1042  * Populate the free space tree by walking the extent tree. Operations on the
1043  * extent tree that happen as a result of writes to the free space tree will go
1044  * through the normal add/remove hooks.
1045  */
1046 static int populate_free_space_tree(struct btrfs_trans_handle *trans,
1047                                     struct btrfs_block_group_cache *block_group)
1048 {
1049         struct btrfs_root *extent_root = trans->fs_info->extent_root;
1050         struct btrfs_path *path, *path2;
1051         struct btrfs_key key;
1052         u64 start, end;
1053         int ret;
1054 
1055         path = btrfs_alloc_path();
1056         if (!path)
1057                 return -ENOMEM;
1058         path->reada = READA_FORWARD;
1059 
1060         path2 = btrfs_alloc_path();
1061         if (!path2) {
1062                 btrfs_free_path(path);
1063                 return -ENOMEM;
1064         }
1065 
1066         ret = add_new_free_space_info(trans, block_group, path2);
1067         if (ret)
1068                 goto out;
1069 
1070         mutex_lock(&block_group->free_space_lock);
1071 
1072         /*
1073          * Iterate through all of the extent and metadata items in this block
1074          * group, adding the free space between them and the free space at the
1075          * end. Note that EXTENT_ITEM and METADATA_ITEM are less than
1076          * BLOCK_GROUP_ITEM, so an extent may precede the block group that it's
1077          * contained in.
1078          */
1079         key.objectid = block_group->key.objectid;
1080         key.type = BTRFS_EXTENT_ITEM_KEY;
1081         key.offset = 0;
1082 
1083         ret = btrfs_search_slot_for_read(extent_root, &key, path, 1, 0);
1084         if (ret < 0)
1085                 goto out_locked;
1086         ASSERT(ret == 0);
1087 
1088         start = block_group->key.objectid;
1089         end = block_group->key.objectid + block_group->key.offset;
1090         while (1) {
1091                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1092 
1093                 if (key.type == BTRFS_EXTENT_ITEM_KEY ||
1094                     key.type == BTRFS_METADATA_ITEM_KEY) {
1095                         if (key.objectid >= end)
1096                                 break;
1097 
1098                         if (start < key.objectid) {
1099                                 ret = __add_to_free_space_tree(trans,
1100                                                                block_group,
1101                                                                path2, start,
1102                                                                key.objectid -
1103                                                                start);
1104                                 if (ret)
1105                                         goto out_locked;
1106                         }
1107                         start = key.objectid;
1108                         if (key.type == BTRFS_METADATA_ITEM_KEY)
1109                                 start += trans->fs_info->nodesize;
1110                         else
1111                                 start += key.offset;
1112                 } else if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
1113                         if (key.objectid != block_group->key.objectid)
1114                                 break;
1115                 }
1116 
1117                 ret = btrfs_next_item(extent_root, path);
1118                 if (ret < 0)
1119                         goto out_locked;
1120                 if (ret)
1121                         break;
1122         }
1123         if (start < end) {
1124                 ret = __add_to_free_space_tree(trans, block_group, path2,
1125                                                start, end - start);
1126                 if (ret)
1127                         goto out_locked;
1128         }
1129 
1130         ret = 0;
1131 out_locked:
1132         mutex_unlock(&block_group->free_space_lock);
1133 out:
1134         btrfs_free_path(path2);
1135         btrfs_free_path(path);
1136         return ret;
1137 }
1138 
1139 int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
1140 {
1141         struct btrfs_trans_handle *trans;
1142         struct btrfs_root *tree_root = fs_info->tree_root;
1143         struct btrfs_root *free_space_root;
1144         struct btrfs_block_group_cache *block_group;
1145         struct rb_node *node;
1146         int ret;
1147 
1148         trans = btrfs_start_transaction(tree_root, 0);
1149         if (IS_ERR(trans))
1150                 return PTR_ERR(trans);
1151 
1152         set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1153         free_space_root = btrfs_create_tree(trans, fs_info,
1154                                             BTRFS_FREE_SPACE_TREE_OBJECTID);
1155         if (IS_ERR(free_space_root)) {
1156                 ret = PTR_ERR(free_space_root);
1157                 goto abort;
1158         }
1159         fs_info->free_space_root = free_space_root;
1160 
1161         node = rb_first(&fs_info->block_group_cache_tree);
1162         while (node) {
1163                 block_group = rb_entry(node, struct btrfs_block_group_cache,
1164                                        cache_node);
1165                 ret = populate_free_space_tree(trans, block_group);
1166                 if (ret)
1167                         goto abort;
1168                 node = rb_next(node);
1169         }
1170 
1171         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1172         btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1173         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1174 
1175         return btrfs_commit_transaction(trans);
1176 
1177 abort:
1178         clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
1179         btrfs_abort_transaction(trans, ret);
1180         btrfs_end_transaction(trans);
1181         return ret;
1182 }
1183 
1184 static int clear_free_space_tree(struct btrfs_trans_handle *trans,
1185                                  struct btrfs_root *root)
1186 {
1187         struct btrfs_path *path;
1188         struct btrfs_key key;
1189         int nr;
1190         int ret;
1191 
1192         path = btrfs_alloc_path();
1193         if (!path)
1194                 return -ENOMEM;
1195 
1196         path->leave_spinning = 1;
1197 
1198         key.objectid = 0;
1199         key.type = 0;
1200         key.offset = 0;
1201 
1202         while (1) {
1203                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
1204                 if (ret < 0)
1205                         goto out;
1206 
1207                 nr = btrfs_header_nritems(path->nodes[0]);
1208                 if (!nr)
1209                         break;
1210 
1211                 path->slots[0] = 0;
1212                 ret = btrfs_del_items(trans, root, path, 0, nr);
1213                 if (ret)
1214                         goto out;
1215 
1216                 btrfs_release_path(path);
1217         }
1218 
1219         ret = 0;
1220 out:
1221         btrfs_free_path(path);
1222         return ret;
1223 }
1224 
1225 int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
1226 {
1227         struct btrfs_trans_handle *trans;
1228         struct btrfs_root *tree_root = fs_info->tree_root;
1229         struct btrfs_root *free_space_root = fs_info->free_space_root;
1230         int ret;
1231 
1232         trans = btrfs_start_transaction(tree_root, 0);
1233         if (IS_ERR(trans))
1234                 return PTR_ERR(trans);
1235 
1236         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
1237         btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
1238         fs_info->free_space_root = NULL;
1239 
1240         ret = clear_free_space_tree(trans, free_space_root);
1241         if (ret)
1242                 goto abort;
1243 
1244         ret = btrfs_del_root(trans, &free_space_root->root_key);
1245         if (ret)
1246                 goto abort;
1247 
1248         list_del(&free_space_root->dirty_list);
1249 
1250         btrfs_tree_lock(free_space_root->node);
1251         clean_tree_block(fs_info, free_space_root->node);
1252         btrfs_tree_unlock(free_space_root->node);
1253         btrfs_free_tree_block(trans, free_space_root, free_space_root->node,
1254                               0, 1);
1255 
1256         free_extent_buffer(free_space_root->node);
1257         free_extent_buffer(free_space_root->commit_root);
1258         kfree(free_space_root);
1259 
1260         return btrfs_commit_transaction(trans);
1261 
1262 abort:
1263         btrfs_abort_transaction(trans, ret);
1264         btrfs_end_transaction(trans);
1265         return ret;
1266 }
1267 
1268 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
1269                                         struct btrfs_block_group_cache *block_group,
1270                                         struct btrfs_path *path)
1271 {
1272         int ret;
1273 
1274         block_group->needs_free_space = 0;
1275 
1276         ret = add_new_free_space_info(trans, block_group, path);
1277         if (ret)
1278                 return ret;
1279 
1280         return __add_to_free_space_tree(trans, block_group, path,
1281                                         block_group->key.objectid,
1282                                         block_group->key.offset);
1283 }
1284 
1285 int add_block_group_free_space(struct btrfs_trans_handle *trans,
1286                                struct btrfs_block_group_cache *block_group)
1287 {
1288         struct btrfs_fs_info *fs_info = trans->fs_info;
1289         struct btrfs_path *path = NULL;
1290         int ret = 0;
1291 
1292         if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
1293                 return 0;
1294 
1295         mutex_lock(&block_group->free_space_lock);
1296         if (!block_group->needs_free_space)
1297                 goto out;
1298 
1299         path = btrfs_alloc_path();
1300         if (!path) {
1301                 ret = -ENOMEM;
1302                 goto out;
1303         }
1304 
1305         ret = __add_block_group_free_space(trans, block_group, path);
1306 
1307 out:
1308         btrfs_free_path(path);
1309         mutex_unlock(&block_group->free_space_lock);
1310         if (ret)
1311                 btrfs_abort_transaction(trans, ret);
1312         return ret;
1313 }
1314 
1315 int remove_block_group_free_space(struct btrfs_trans_handle *trans,
1316                                   struct btrfs_block_group_cache *block_group)
1317 {
1318         struct btrfs_root *root = trans->fs_info->free_space_root;
1319         struct btrfs_path *path;
1320         struct btrfs_key key, found_key;
1321         struct extent_buffer *leaf;
1322         u64 start, end;
1323         int done = 0, nr;
1324         int ret;
1325 
1326         if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
1327                 return 0;
1328 
1329         if (block_group->needs_free_space) {
1330                 /* We never added this block group to the free space tree. */
1331                 return 0;
1332         }
1333 
1334         path = btrfs_alloc_path();
1335         if (!path) {
1336                 ret = -ENOMEM;
1337                 goto out;
1338         }
1339 
1340         start = block_group->key.objectid;
1341         end = block_group->key.objectid + block_group->key.offset;
1342 
1343         key.objectid = end - 1;
1344         key.type = (u8)-1;
1345         key.offset = (u64)-1;
1346 
1347         while (!done) {
1348                 ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
1349                 if (ret)
1350                         goto out;
1351 
1352                 leaf = path->nodes[0];
1353                 nr = 0;
1354                 path->slots[0]++;
1355                 while (path->slots[0] > 0) {
1356                         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
1357 
1358                         if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
1359                                 ASSERT(found_key.objectid == block_group->key.objectid);
1360                                 ASSERT(found_key.offset == block_group->key.offset);
1361                                 done = 1;
1362                                 nr++;
1363                                 path->slots[0]--;
1364                                 break;
1365                         } else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY ||
1366                                    found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
1367                                 ASSERT(found_key.objectid >= start);
1368                                 ASSERT(found_key.objectid < end);
1369                                 ASSERT(found_key.objectid + found_key.offset <= end);
1370                                 nr++;
1371                                 path->slots[0]--;
1372                         } else {
1373                                 ASSERT(0);
1374                         }
1375                 }
1376 
1377                 ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
1378                 if (ret)
1379                         goto out;
1380                 btrfs_release_path(path);
1381         }
1382 
1383         ret = 0;
1384 out:
1385         btrfs_free_path(path);
1386         if (ret)
1387                 btrfs_abort_transaction(trans, ret);
1388         return ret;
1389 }
1390 
1391 static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
1392                                    struct btrfs_path *path,
1393                                    u32 expected_extent_count)
1394 {
1395         struct btrfs_block_group_cache *block_group;
1396         struct btrfs_fs_info *fs_info;
1397         struct btrfs_root *root;
1398         struct btrfs_key key;
1399         int prev_bit = 0, bit;
1400         /* Initialize to silence GCC. */
1401         u64 extent_start = 0;
1402         u64 end, offset;
1403         u64 total_found = 0;
1404         u32 extent_count = 0;
1405         int ret;
1406 
1407         block_group = caching_ctl->block_group;
1408         fs_info = block_group->fs_info;
1409         root = fs_info->free_space_root;
1410 
1411         end = block_group->key.objectid + block_group->key.offset;
1412 
1413         while (1) {
1414                 ret = btrfs_next_item(root, path);
1415                 if (ret < 0)
1416                         goto out;
1417                 if (ret)
1418                         break;
1419 
1420                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1421 
1422                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1423                         break;
1424 
1425                 ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
1426                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1427 
1428                 caching_ctl->progress = key.objectid;
1429 
1430                 offset = key.objectid;
1431                 while (offset < key.objectid + key.offset) {
1432                         bit = free_space_test_bit(block_group, path, offset);
1433                         if (prev_bit == 0 && bit == 1) {
1434                                 extent_start = offset;
1435                         } else if (prev_bit == 1 && bit == 0) {
1436                                 total_found += add_new_free_space(block_group,
1437                                                                   extent_start,
1438                                                                   offset);
1439                                 if (total_found > CACHING_CTL_WAKE_UP) {
1440                                         total_found = 0;
1441                                         wake_up(&caching_ctl->wait);
1442                                 }
1443                                 extent_count++;
1444                         }
1445                         prev_bit = bit;
1446                         offset += fs_info->sectorsize;
1447                 }
1448         }
1449         if (prev_bit == 1) {
1450                 total_found += add_new_free_space(block_group, extent_start,
1451                                                   end);
1452                 extent_count++;
1453         }
1454 
1455         if (extent_count != expected_extent_count) {
1456                 btrfs_err(fs_info,
1457                           "incorrect extent count for %llu; counted %u, expected %u",
1458                           block_group->key.objectid, extent_count,
1459                           expected_extent_count);
1460                 ASSERT(0);
1461                 ret = -EIO;
1462                 goto out;
1463         }
1464 
1465         caching_ctl->progress = (u64)-1;
1466 
1467         ret = 0;
1468 out:
1469         return ret;
1470 }
1471 
1472 static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
1473                                    struct btrfs_path *path,
1474                                    u32 expected_extent_count)
1475 {
1476         struct btrfs_block_group_cache *block_group;
1477         struct btrfs_fs_info *fs_info;
1478         struct btrfs_root *root;
1479         struct btrfs_key key;
1480         u64 end;
1481         u64 total_found = 0;
1482         u32 extent_count = 0;
1483         int ret;
1484 
1485         block_group = caching_ctl->block_group;
1486         fs_info = block_group->fs_info;
1487         root = fs_info->free_space_root;
1488 
1489         end = block_group->key.objectid + block_group->key.offset;
1490 
1491         while (1) {
1492                 ret = btrfs_next_item(root, path);
1493                 if (ret < 0)
1494                         goto out;
1495                 if (ret)
1496                         break;
1497 
1498                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
1499 
1500                 if (key.type == BTRFS_FREE_SPACE_INFO_KEY)
1501                         break;
1502 
1503                 ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
1504                 ASSERT(key.objectid < end && key.objectid + key.offset <= end);
1505 
1506                 caching_ctl->progress = key.objectid;
1507 
1508                 total_found += add_new_free_space(block_group, key.objectid,
1509                                                   key.objectid + key.offset);
1510                 if (total_found > CACHING_CTL_WAKE_UP) {
1511                         total_found = 0;
1512                         wake_up(&caching_ctl->wait);
1513                 }
1514                 extent_count++;
1515         }
1516 
1517         if (extent_count != expected_extent_count) {
1518                 btrfs_err(fs_info,
1519                           "incorrect extent count for %llu; counted %u, expected %u",
1520                           block_group->key.objectid, extent_count,
1521                           expected_extent_count);
1522                 ASSERT(0);
1523                 ret = -EIO;
1524                 goto out;
1525         }
1526 
1527         caching_ctl->progress = (u64)-1;
1528 
1529         ret = 0;
1530 out:
1531         return ret;
1532 }
1533 
1534 int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
1535 {
1536         struct btrfs_block_group_cache *block_group;
1537         struct btrfs_fs_info *fs_info;
1538         struct btrfs_free_space_info *info;
1539         struct btrfs_path *path;
1540         u32 extent_count, flags;
1541         int ret;
1542 
1543         block_group = caching_ctl->block_group;
1544         fs_info = block_group->fs_info;
1545 
1546         path = btrfs_alloc_path();
1547         if (!path)
1548                 return -ENOMEM;
1549 
1550         /*
1551          * Just like caching_thread() doesn't want to deadlock on the extent
1552          * tree, we don't want to deadlock on the free space tree.
1553          */
1554         path->skip_locking = 1;
1555         path->search_commit_root = 1;
1556         path->reada = READA_FORWARD;
1557 
1558         info = search_free_space_info(NULL, fs_info, block_group, path, 0);
1559         if (IS_ERR(info)) {
1560                 ret = PTR_ERR(info);
1561                 goto out;
1562         }
1563         extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
1564         flags = btrfs_free_space_flags(path->nodes[0], info);
1565 
1566         /*
1567          * We left path pointing to the free space info item, so now
1568          * load_free_space_foo can just iterate through the free space tree from
1569          * there.
1570          */
1571         if (flags & BTRFS_FREE_SPACE_USING_BITMAPS)
1572                 ret = load_free_space_bitmaps(caching_ctl, path, extent_count);
1573         else
1574                 ret = load_free_space_extents(caching_ctl, path, extent_count);
1575 
1576 out:
1577         btrfs_free_path(path);
1578         return ret;
1579 }
1580 

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